Boiler cleaner tube



Feb. 16, 1937. w UNAKER 2,070,795

BOILER CLEANER TUBE Filed Nov. 28, 1934 FIG. I.

I N VE N TOR fic'deric/f M Lina/fer;

a v ArroRNEY Patented Feb. 16, 1937 UNITED STATES PATENT OFFICE BOILER CLEANER TUBE Frederick W. Linaker, St. Louis, Mo. Application November 28, 1934, Serial No. 755,137

1 Claim.

My invention has relation to improvements in boiler cleaner tubes for operation within the combustion spaces ofthe boiler furnace, and it consists in the novel features of construction more fully set forth in the specification and pointed out in the claim.

The object of the invention is to provide a boiler cleaner tube that will withstand the higher temperatures attained in certain parts of the boiler passes, and continue to function properly over prolonged periods of time in such temperatures which often exceed 2000 F. in high pressure boilers.

In addition to the high temperatures the boiler cleaner tube must also withstand the destructive effect of the corrosive furnace gases which produce scale. In other words, the tube must have a high resistance to scaling so as to have a reasonably long life. Then, too, an ideal boiler cleaner tube should retain its tensile strength in the high temperatures in which it operates and should not undergo appreciable chemical or physical change. Tubes now in use are not quite satisfactory in this particular as they are made of alloys which become brittle on continued exposure to the high temperatures of the boiler furnace due to grain growth and other causes.

Much effort has been expended by the industry to produce ideal tubes for boiler cleaners and many different alloys have been used in their manufacture, but none has yet proven entirely satisfactory, although progress has been made; and the chromium-iron alloy tubes now in general use are a vast improvement over the steel tubes with which the boiler cleaner manufacturers started.

However, one defect in the chromium-iron alloy tube is that it becomes brittle after continued exposure to the high temperatures (in the region of 1750 F.) under which it must function. This is especially true if the chromium content is high enough (approximately 22%) to give the desired scale resisting properties.

The advantages of my invention will be better apparent from a detailed description of the same in connection with the accompanying drawing, in which:

Figure 1 is a side elevation of a boiler cleaner attached to a boiler and embodying my improved cleaner tube; Fig. 2 is a side elevation of a cleaner tube with parts broken away wrought from an alloy of iron-chromium and nickel in the proportion hereinafter set forth; Fig. 3 shows a part of a boiler cleaner tube in longitudinal section, said tube being made up of cast sections welded together and formed of the alloy hereinafter ex plained as being most desirable for this type of tube; and Fig. 4 is a part of a boiler cleaner tube shown in longitudinal section comprising an inner element formed of a nickel-chromium-iron alloy and having an outer covering or layer of chromium which may be applied thereto in any known manner.

I have discovered that an alloy of iron, chromium, and nickel in certain proportions (pointed out below) is not only scale resistant to the action of the furnace gases but also resists the changes in the structure of the metal which produce brittleness in the iron-chromium alloys 'now in use.

The nickel content of the alloy of which my improved boiler cleaner tube is made must be substantial; in fact, considerably greater than the 2% or 3% that is now tolerated in boiler cleaner tubes made of iron-chromium alloys. One example of the composition of the alloy of a boiler cleaner tube according to my invention is as follows:

Per cent Nickel Chromium 14 Iron 6 In the above analysis negligible quantities of other elements present as impurities are disregarded. However, it is obvious that in the com mercial production of the alloy the presence of impurities would slightly alter the above per- The above examples show that as the nickel content decreases the chromium content also decreases but the iron increases. Other proportions of the metals comprising the alloy can be sa isfactorily used in tubes that are not wrought.

However, regard must be had for the workability of the allow when the tubes are to be drawn seamless. The above proportions are ideal for wrought tubes.

In casting the tubes I have found that the most satisfactory results are obtained from alloys having the following analyses:

Percent Iron 50 Chromium 32 Nickel ..I .I V 18 Total 10o Percent Iron 60 Chromium 26 Nickel Total 100 I P b ht Iron 74 Chromium L 18 Nickel 8 Total r An alloy having the intermediate analysis ispreferable for boiler cleaner tubes as they possess the required properties to the greatest extent.

If tubes made of; alloys above described are subjected for extended periods to atmospheres rich in sulphur, scaling will occur. F'or this reason I protect the surfaces of the tubewith a covering of chromium. Preferably, the chromium is plated on the tube although the same results may be obtained by galvanizing,- dipping, or by a jacket or sheath of chromium or high chromium content chromium-iron alloy.

Soot blower tubes made of the above described alloys possess high scale resisting properties and are also tough and ductile. Furthermore, they do not become brittle under prolonged high temperature service to the extent of becoming unserviceable.

Referring to the drawing, B represents a frag- 'ment of a boiler through an opening Oin the wall W of which passes the boiler cleaner tube I, the outer end of which has connection with the operating head A, as Well understood in the art. The boiler cleaner tube l traverses the boiler tubes T and is exposed to the corrosive action of the furnace heat and products of combustion. The tube I must therefore not only be heat resisting in the sense of retaining its tensile strength under high temperature, but must also be able to resist the corrosive action of the gases. For this reason my improved tube is wrought from the alloy of chromium, iron and nickel, as above explained.

I Under certain conditions it may be desirable that a cast tube 2, as shown in Fig. 3, be used insteadof a wrought tube. The tube is preferably cast in sections 2, 2, 2, which sections are welded together as shown at 3, the welds being formed with the aid of the same alloy as that of the tube sections so that after the sections are welded together the tube will be homogeneous from end to end and be :free "of joints orlinesof cleavage.

In order to increase the scale resistance of the tube within the furnace atmosphere a tube 4 may be made of two elements, an inner element 5 either wrought or cast as just described, and an outer element 6 comprising a layer or covering over the inner element, saidcovering preferably consisting of chromium since chromium has the property of resisting to a very great extent the corrosive action of furnace gases. This layer 6 may be plated over the inner element 5 or applied in any other known manner as the essential requisite is that it cover and protect the inner tube 5 from the action of the gases and has nothing to do with the strength or other properties of the tube.

Having described my invention, I claim':

A boiler cleaner tube cast from an alloy of iron, nickel and chromium, the chromium content being sufiicient to resist scaling when the tube is subjected to the destructive gases of the boiler furnace, and the nickel content being suflicient to give the tube the property of resisting the changes in its grain structure when subjected to the high temperatures prevailing within the furnace.

' FREDERICK W; LINAKER. 

